Please help - understanding my heating / hot water system

molerat

11 means you are being billed for a metric meter, that is roughly how many kWh there is in a cu m of gas.  If the answer is 32 then you are being incorrectly billed as an imperial meter so being charged 2.83 times the correct amount.  This is the first and simplest thing to check in a high gas bill scenario.

Fishandchips80

@molerat Ah, I see, thanks for explaining. Ok, so ours is indeed 11. I hope reducing the hot water schedule will still make somewhat of a difference, because we do run quite a bit of water in this house (3 kids), so if the hot water has run out then we make do with cold during the day until it heats up again for bathtime (just as would’ve been the case in our last house). In this house, the hot water has seemingly been unlimited, so it seems that might have contributed to the high bill

Bendo

You don't know the bill is high yet do you as all your reads are estimates (unless I've missed a post). Until you have some real reads over period, you are just guessing. 

Albermarle

molerat said:

Having the water on for long periods should not cost that much unless you are constantly running the hot tap.  I found that even having it on for up to 15 hours only used a maximum of around 15 kWh a day so 75p or £23 per month.  Check your bill and divide the kWh charged by the gas units billed, the answer should be around 11.

There should be a thermostat on the side of the tank, check that is not screwed up to max.

One thing to help with your understanding of how it all works is that those controllers do not turn the boiler on, they simply tell the relevant valve to open and the open microswitch in the valve motor head calls for heat from the boiler.  The HW on command should pass through the tank stat then on to the valve.

OP - The hot water tank will have its own separate thermostat sticking out of the side of the tank.
Can you find it please and see what it is set to. 

oldagetraveller1

https://www.plumbnation.co.uk/worcester-greenstar-4000-30kw-combination-boiler-natural-gas-10-5434?utm_source=organic&utm_medium=shoppingfeed&utm_campaign=bingshopping&msclkid=1b1469496dbb1d60a690000bd3c3f6f3&utm_source=bing&utm_medium=cpc&utm_campaign=Shopping - All Boilers&utm_term=4584001449349521&utm_content=All Boilers

Looking at the picture of the OP's boiler and at Worcester boilers it looks very much like that in the link - a combination boiler. The round display, at the bottom, clearly shows symbols for heating and hot water.

QrizB

The Greenstar 4000 is also available as a system boiler, which looks identical:

https://www.worcester-bosch.co.uk/products/boilers/directory/greenstar-4000-system

The Greenstar 8000+ regular boiler looks pretty similar, too:

https://www.worcester-bosch.co.uk/products/boilers/directory/greenstar-8000-regular

matelodave

As @QrizB suggest its more likely to be a system or regular boiler than a combi as its got a hot water tank. To refine it further a system boiler usually has a non vented tank (like yours has) whereas a regular boiler would normally be vented with a tank in the loft

@Albermarle has asked if you have a tank thermostat, can you confirm that you have one fitted and what it has been set to. Likewise what temperature does the boiler display show when its running.

QrizB

The HW tank is one of these:

https://www.cityplumbing.co.uk/p/kingspan-albion-ultrasteel-slimline-180-litre-indirect-unvented-cylinder-aui180slmerp/p/902649

Page 3 of this pdf suggests there is a dry thermostat pocket (item G) in the lower quarter of the tank:

https://www.fueltankshop.co.uk/files/pdf/1593_kingspan-albion-ultrasteel-brochure-en-gb-21feb2022-v1.pdf

That part of the tank isn't visible in any of the photos that have so far been shared.

Fishandchips80

Sorry - it’s really hard to get a good angle of the hot water tank, but I’ve attached some more photos here that may answer some of the Qs above 

QrizB

The knob on the first photo set halfway between 45 and 55 appears to be your tank thermostat.

If you look at the later photos you've just posted, you can see "-OSTAT" printed on the side of it.